Vancomycin hydrochloride is an amphoteric glycopeptide antibiotic produced by fermentation of the microorganism Nocardia orientalis (or Amycolatopsis orientalis) under controlled conditions, which has a molecular formula C66H75Cl2N9O24.HCl and a molecular weight of 1.486. Commercial distribution of vancomycin hydrochloride began at the end of 1950s and its chloride form has been used clinically ever since. Lyophilized vancomycin hydrochloride is a white or almost white powder. It is hygroscopic, freely soluble in water, and slightly soluble in alcohol. When mixed with water (5%, w/w), vancomycin hydrochloride has a pH between 2.5 and 4.5.
Vancomycin hydrochloride acts by binding the C-terminal D-Ala-D-Ala peptides, which inhibits the synthesis of cell walls and also changes the permeability of cell membranes as well as synthesis of RNA. Vancomycin hydrochloride is particularly used for the initial treatment of serious or severe infections caused by staphylococci resistant to β-lactam antibiotics as well as in patients who are penicillin-sensitive or do not respond to penicillin or cephalosporine. Vancomycin hydrochloride is commercially available in oral (solution and capsules/pulvules) and parenteral (sterile intravenous solution in vials) forms.
Vancomycin hydrochloride, alone or in combination with other aminoglycosides, is useful in treating staphylococcal, streptococcal, enterococcal or diphtherial endocarditis. An indication of oral vancomycin therapy includes the treatment of pseudomembranous colitis caused by staphylococci when it is unresponsive to vancomycin for injection. Vancomycin for injection may be applicable to all of the other indications.
A vancomycin molecule is composed of two basic structures, including a saccharide group, α-o-vancosamine-β-o-glucosyl, and a heptapeptide backbone. The structure of vancomycin determines its instability and the case with which it may be degraded under acidic conditions, alkaline conditions and/or high temperature conditions. Normally, degradation products have no biological activity, so side effects may be reduced when impurity levels are significantly reduced.
Desvancosaminyl vancomycin and aglucovancomycin are degradation products that result from the loss of the disaccharide moiety and the vancosamine sugar, respectively, under acidic and high temperature conditions. Vancomycin can be degraded into another degradation product, desamidovancomycin, by hydrolytic loss of ammonia in weak acid conditions. Desamidovancomycin exists in two isomeric forms as shown in FIGS. 1 and 2. The forming mechanism of desamidovancomycin has been described in publications, such as, for example, “Vancomycin degradation products as potential chiral selectors in enantiomeric separation of racemic compounds,” by Alireza Ghassempour, Journal of Chromatography A, 1191 (2008) 182-187. In this publication, the authors deduced that there are two pathways for vancomycin to succinimide and its conversion to desamidovancomycin, as described in FIG. 3.
Industrial methods for preparing vancomycin hydrochloride have been known for some time. For instance, U.S. Pat. No. 3,067,099 discloses a method of producing vancomycin through cultivation of a vancomycin-producing strain of Streptomyces Orientalis under aerobic conditions in a culture medium containing assimilable sources of carbohydrate, organic nitrogen and inorganic salts. Separation and purification processes for separating vancomycin hydrochloride from fermentation broth have also been disclosed in literature and patent documents. U.S. Pat. No. 4,440,753 describes an example of an isolation method and purification process for forming precipitate by isopropanol, ethanol or acetone. U.S. Pat. No. 4,868,285 discloses an example of an isolation method and filtration process to collect a compound of imidazole and vancomycin. However, in many of these processes, formed nantokite or imidazole compound may decompose and contaminate the final vancomycin product. Further, slurry may form when using isopropanol, ethanol or acetone to isolate vancomycin, which is hard to filter.
U.S. Pat. No. 5,853,720 discloses a process for purifying vancomycin hydrochloride that combines the preparative chromatography on a silica gel column containing an alkaline water-methanol mobile phase and the precipitation with ethanol from a salt-water-ethanolic solution. The process produces vancomycin hydrochloride solid by lyophilization, spray drying or precipitation of pH 3, 100 g/L concentrate, which is obtained through a series of operations like micro-filtration of vancomycin broth, then macro porous resin adsorption and elution, concentration and desalting, discoloring with activated carbon. The vancomycin solution is spray dried at an inlet temperature of 115-130° C. and an outlet temperature of 85±5° C. Usually, the content of water in vancomycin hydrochloride is about 4%, therefore it has been practice to additionally dry vancomycin hydrochloride in a rotation vacuum dryer at a temperature of 45-50° C. to obtain a dry solid product. This patent mentions that a chromatographic purity of vancomycin hydrochloride solution is about 93%. However, the patent does not appear to indicate the chromatographic purity and impurity levels of the final dry product. Experts and experienced technicians can appreciate that chromatographic purity of the obtained vancomycin hydrochloride product may decrease significantly after spray drying under high temperature conditions and vacuum drying at medium temperature conditions, resulting in increased impurity level and darker product color.
U.S. Pat. No. 7,018,804 discloses a method for preparing high purity vancomycin hydrochloride. In this patent, vancomycin hydrochloride concentrate with a HPLC purity of not less than 95% based on the EP method is obtained through a series of column purification processes, including strong acid type ion exchange resin chromatography, weak base type ion exchange resin column and aluminum oxide column chromatography, and hydrophobic resin chromatography. The final vancomycin hydrochloride product is obtained through precipitation by adding multiple (e.g., 5) times volumes of acetone and drying the resultant solution under vacuum conditions at a temperature of 40° C. It is note that this drying method would likely elevate the impurity level in the final product. Moreover, using the described method, residual solvents can't be removed completely to meet the corresponding requirements of, e.g., the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH).
M. Nieto and H. R. Perkins, in their publication, “Physicochemical Properties of Vancomycin and Iodovancomycin and their Complexes with Diacetyl-L-lysyl-D-alanyl-D-alanine,” Biochem. J. (1971) 123, 773-787, observed aggregation of vancomycin in an aqueous solution. The structure of aggregated glycopeptides remained uncharacterized. The publication described that aggregation is influenced by many factors such as ionization degree of phenol, hydrogen bond, etc.
Through addition of appropriate excipients such as surfactants or carbohydrates to reduce the forming of aggregates, the limiting concentration of vancomycin hydrochloride in water can be increased.
Due to thermal instability of vancomycin hydrochloride, the solution is typically prepared at a relative low temperature to avoid an increase in impurity level. Even if the solution is dried at a low temperature and under high vacuum conditions, the chromatographic purity of vancomycin hydrochloride will inevitably decrease. The lyophilization at low temperature will cause chromatographic purity to decrease by about 0.5% or more. For instance, the purity level of the solution will decrease by more than 1.0% through vacuum drying at 40° C. within 8 hours. The mainly-increased impurity is desamidovancomycin.
U.S. Pat. No. 6,001,800 discloses a method for preparing spray dried erythropoietin, and the dry erythropoietin powder produced thereby. The patent discloses that through addition of mannitol, glycine and sodium citrate as stabilizers and dispersants, active substances with appropriate ranges of particle size can be obtained.
U.S. Pat. No. 6,479,049 discloses a method and composition for the dry powder formulation of cytokines, especially interferons. The patent mentions interferon, to which carbohydrates, polypeptides and amino acids are added as a carrier. Appropriate excipients are added to improve product stability.
Excipients were reported to be used in vancomycin hydrochloride intravenous infusion in order to improve vancomycin stability and solubility such as Meek, a lyophilized generic product containing 100 mg each of D-mannitol and PEG 400 per 500 mg of vancomycin hydrochloride injection. Moreover, it was also reported that Meek was less nephrotoxic than a conventional preparation without addition of excipients, as noted by Naoko Hodoshima, Drug Metab. Pharmacokin. 19(1): 68-75 (2004).
U.S. Patent Application Publication No. US 2013/0009330 discloses a preparative method of a stable and easily-soluble powdered vancomycin formulation for injection through a spray drying process after dissolving a mixture of 10-20% by weight vancomycin HCl, about 2-4% by weight PEG, and 2-4% by weight mannitol. However, impurity B specified in European Pharmacopeia can't be significantly controlled by using this formulation. Moreover, the concentration of the vancomycin hydrochloride solution is limited at 10-20%, and it is not easy for further filling of spray dried powder due to low density.
Presently, drying methods used for drying vancomycin hydrochloride include lyophilization, vacuum drying and spray drying.
Lyophilization tends to be the main drying process for the production of both preparations and active substances. During lyophilization of active substances, it is difficult to ensure application of aseptic technology at each stage of the production process, including, e.g., during loading, unloading and powder collection processes, thereby making it very difficult to obtain sterile active substances. Therefore, it is frequently necessary to repeatedly dissolve non-sterile active substances and lyophilize the substances to get sterile powder for injection in vials. This inefficient production process results in large investments in specialized equipment, low production yields, poor efficiency and high operation costs, which may not be applicable for the production of large strengths above, e.g., 10 g/vial because of the high ratio of vials that tend to break during the process, as well as the undesirably long lyophilization cycle. The prolonged production cycle tends to affect product quality due to a higher impurity level.
If using vacuum drying, as a heat-sensitive substance, vancomycin should be dried at a low temperature and under high vacuum conditions. However, because vancomycin tends to combine with water and some polar solvent, it is hard to completely remove the water or the polar solvent. A significant problem in vacuum drying is that the residual solvent level can't meet the ICH's requirements. Moreover, prolonged drying time will result in a higher impurity level.
There has been discussion of using spray drying in industrial production of vancomycin hydrochloride under high temperature conditions. In spray drying, a vancomycin hydrochloride fluid solution is transformed into a dry-form product by spraying the solution into, e.g., a heat drying device. The resultant spray-dried product is typically in powder form. Spray drying, however, can result in degradation of vancomycin hydrochloride. During preparation of the vancomycin chloride solution, vancomycin chloride concentration levels can exceed 20%, thereby increasing the viscosity of the solution and forming an aggregate (e.g., semi-solid jelly) or precipitate that may block equipment, e.g., production filters. The implementation of 15% vancomycin hydrochloride concentration levels has been reported, such as, e.g., in US2013009330.
Solution stability should be considered since the concentrate may be stored for more than twenty-four hours because additional preparation time may be required for each operation. There exists the unsolved problem in industrial production on how to ensure stability of vancomycin hydrochloride solution without increasing impurity and forming precipitate within, for example, forty-eight hours. Since the temperature during spray drying may exceed above 80° C., ensuring the stability of vancomycin hydrochloride may be a barrier to production.
A further problem with spray drying is that the spray dried vancomycin powder will be filled directly into, e.g., vials. Accordingly, the process should allow for reconstitution time at least as fast as the lyophilized formulations. Spray dried vancomycin tends to have smaller particle sizes and the reconstitution time tends to be longer than that of the loose-structured lyophilized product.
In order to reduce the possibility of side effects, a high chromatographic purity of antibiotics is very important in certain applications, which cannot be achieved by hitherto purification processes.
The present disclosure provides a novel system and a novel method for producing high purity and high potency vancomycin hydrochloride that solve the afore-discussed problems.